SYNOPSIS

DESCRIPTION

Help parsing or adding trailers lines, that look similar to RFC 822 e-mail
headers, at the end of the otherwise free-form part of a commit
message.

This command reads some patches or commit messages from either the
<file> arguments or the standard input if no <file> is specified. If
--parse is specified, the output consists of the parsed trailers.

Otherwise, this command applies the arguments passed using the
--trailer option, if any, to the commit message part of each input
file. The result is emitted on the standard output.

Some configuration variables control the way the --trailer arguments
are applied to each commit message and the way any existing trailer in
the commit message is changed. They also make it possible to
automatically add some trailers.

By default, a <token>=<value> or <token>:<value> argument given
using --trailer will be appended after the existing trailers only if
the last trailer has a different (<token>, <value>) pair (or if there
is no existing trailer). The <token> and <value> parts will be trimmed
to remove starting and trailing whitespace, and the resulting trimmed
<token> and <value> will appear in the message like this:

token: value

This means that the trimmed <token> and <value> will be separated by
': ' (one colon followed by one space).

By default the new trailer will appear at the end of all the existing
trailers. If there is no existing trailer, the new trailer will appear
after the commit message part of the output, and, if there is no line
with only spaces at the end of the commit message part, one blank line
will be added before the new trailer.

Existing trailers are extracted from the input message by looking for
a group of one or more lines that (i) is all trailers, or (ii) contains at
least one Git-generated or user-configured trailer and consists of at
least 25% trailers.
The group must be preceded by one or more empty (or whitespace-only) lines.
The group must either be at the end of the message or be the last
non-whitespace lines before a line that starts with ---. Such three
minus signs start the patch part of the message.

When reading trailers, there can be whitespaces after the
token, the separator and the value. There can also be whitespaces
inside the token and the value. The value may be split over multiple lines with
each subsequent line starting with whitespace, like the "folding" in RFC 822.

Note that trailers do not follow and are not intended to follow many
rules for RFC 822 headers. For example they do not follow
the encoding rules and probably many other rules.

OPTIONS

--in-place

Edit the files in place.

--trim-empty

If the <value> part of any trailer contains only whitespace,
the whole trailer will be removed from the resulting message.
This applies to existing trailers as well as new trailers.

--trailer <token>[(=|:)<value>]

Specify a (<token>, <value>) pair that should be applied as a
trailer to the input messages. See the description of this
command.

--where <placement>

--no-where

Specify where all new trailers will be added. A setting
provided with --where overrides all configuration variables
and applies to all --trailer options until the next occurrence of
--where or --no-where. Possible values are after, before,
end or start.

--if-exists <action>

--no-if-exists

Specify what action will be performed when there is already at
least one trailer with the same <token> in the message. A setting
provided with --if-exists overrides all configuration variables
and applies to all --trailer options until the next occurrence of
--if-exists or --no-if-exists. Possible actions are addIfDifferent,
addIfDifferentNeighbor, add, replace and doNothing.

--if-missing <action>

--no-if-missing

Specify what action will be performed when there is no other
trailer with the same <token> in the message. A setting
provided with --if-missing overrides all configuration variables
and applies to all --trailer options until the next occurrence of
--if-missing or --no-if-missing. Possible actions are doNothing
or add.

--only-trailers

Output only the trailers, not any other parts of the input.

--only-input

Output only trailers that exist in the input; do not add any
from the command-line or by following configured trailer.*
rules.

--unfold

Remove any whitespace-continuation in trailers, so that each
trailer appears on a line by itself with its full content.

--parse

A convenience alias for --only-trailers --only-input
--unfold.

CONFIGURATION VARIABLES

trailer.separators

This option tells which characters are recognized as trailer
separators. By default only : is recognized as a trailer
separator, except that = is always accepted on the command
line for compatibility with other git commands.

The first character given by this option will be the default character
used when another separator is not specified in the config for this
trailer.

For example, if the value for this option is "%=$", then only lines
using the format <token><sep><value> with <sep> containing %, =
or $ and then spaces will be considered trailers. And % will be
the default separator used, so by default trailers will appear like:
<token>% <value> (one percent sign and one space will appear between
the token and the value).

trailer.where

This option tells where a new trailer will be added.

This can be end, which is the default, start, after or before.

If it is end, then each new trailer will appear at the end of the
existing trailers.

If it is start, then each new trailer will appear at the start,
instead of the end, of the existing trailers.

If it is after, then each new trailer will appear just after the
last trailer with the same <token>.

If it is before, then each new trailer will appear just before the
first trailer with the same <token>.

trailer.ifexists

This option makes it possible to choose what action will be
performed when there is already at least one trailer with the
same <token> in the message.

The valid values for this option are: addIfDifferentNeighbor (this
is the default), addIfDifferent, add, replace or doNothing.

With addIfDifferentNeighbor, a new trailer will be added only if no
trailer with the same (<token>, <value>) pair is above or below the line
where the new trailer will be added.

With addIfDifferent, a new trailer will be added only if no trailer
with the same (<token>, <value>) pair is already in the message.

With add, a new trailer will be added, even if some trailers with
the same (<token>, <value>) pair are already in the message.

With replace, an existing trailer with the same <token> will be
deleted and the new trailer will be added. The deleted trailer will be
the closest one (with the same <token>) to the place where the new one
will be added.

With doNothing, nothing will be done; that is no new trailer will be
added if there is already one with the same <token> in the message.

trailer.ifmissing

This option makes it possible to choose what action will be
performed when there is not yet any trailer with the same
<token> in the message.

The valid values for this option are: add (this is the default) and
doNothing.

With add, a new trailer will be added.

With doNothing, nothing will be done.

trailer.<token>.key

This key will be used instead of <token> in the trailer. At
the end of this key, a separator can appear and then some
space characters. By default the only valid separator is :,
but this can be changed using the trailer.separators config
variable.

If there is a separator, then the key will be used instead of both the
<token> and the default separator when adding the trailer.

trailer.<token>.where

This option takes the same values as the trailer.where
configuration variable and it overrides what is specified by
that option for trailers with the specified <token>.

trailer.<token>.ifexists

This option takes the same values as the trailer.ifexists
configuration variable and it overrides what is specified by
that option for trailers with the specified <token>.

trailer.<token>.ifmissing

This option takes the same values as the trailer.ifmissing
configuration variable and it overrides what is specified by
that option for trailers with the specified <token>.

trailer.<token>.command

This option can be used to specify a shell command that will
be called to automatically add or modify a trailer with the
specified <token>.

When this option is specified, the behavior is as if a special
<token>=<value> argument were added at the beginning of the command
line, where <value> is taken to be the standard output of the
specified command with any leading and trailing whitespace trimmed
off.

If the command contains the $ARG string, this string will be
replaced with the <value> part of an existing trailer with the same
<token>, if any, before the command is launched.

If some <token>=<value> arguments are also passed on the command
line, when a trailer.<token>.command is configured, the command will
also be executed for each of these arguments. And the <value> part of
these arguments, if any, will be used to replace the $ARG string in
the command.

EXAMPLES

Configure a sign trailer with a Signed-off-by key, and then
add two of these trailers to a message:

Configure a commit template with some trailers with empty values
(using sed to show and keep the trailing spaces at the end of the
trailers), then configure a commit-msg hook that uses
git interpret-trailers to remove trailers with empty values and
to add a git-version trailer: